Demo version: Bonus levels
Hold 1 + 2 and press A + B at the demo version main menu to play two hidden stages.

Completion bonuses
After getting 120 stars as Mario, you will see an alternate ending. After the credits, you will get Luigi and a Luigi Icon. Luigi is just like Mario, but he jumps higher, runs faster, and has lower traction.

Grand Finale Galaxy
After you get 120 stars as Luigi, you will unlock the Grand Finale Galaxy for both Luigi and Mario, where Star 121 is found after all 100 purple coins are collected.

Assistant
Use a second Wiimote during game play. Although a second player will not appear, the second Wiimote will have its own pointer, allowing another player to assist by collecting items and helping Mario's jumps.

Watermelons instead of coconuts
Collect 9,999 Star Bits in the Hub.

View number of lives lost
Collect the final star in the Grand Finale Galaxy with both Mario and Luigi. The information for your saved game file will now include the number of times you have lost a life.

Flip the screen
Note: You must have the Engine Room dome unlocked. Go outside of the dome. Move slightly to the left. jump off the platform and slide down the curtain. After falling off the curtain, immediately Ground Pound and fall into space. A bubble will carry Mario or Luigi back up to the Engine Room. While he is going up, the screen will flip for about two seconds. Note: This may not work every time.

Rosalina's bubble
Go to where Polara and Rosalina stand together by the beacon. Stand far enough away from Rosalina so that the talk sign does not appear. Then, try to jump on Rosalina. A bubble will form around her.

Attack Rosalina
Go to the room where Rosalina is standing. Zoom in, aim at her, and press B to fire a Star Bit at her. When it hits her she will jump because it scares her, and it will hurt her.

Changing costume when hiding
Become Bee Mario. Your costume will be different than your normal one. Then, walk behind an object such as a wall. You will see a black outline of Mario, however it is of his normal appearance instead of the Bee costume he is currently wearing.

Jump towards the Beacon without being carried back to the platform
Perform a long jump (press Z then A while running) towards the Beacon (the big yellow ball off the platform where Rosalina is standing). If timed correctly, you will land under the Beacon without being carried away until you slide further away from the Beacon.